By Bob Goemans
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Polyp Lab 


 Heterodontus francisci (Horn Shark)

Heterodontus francisci
(Girard, 1854)

Horn Shark

Not Reef Tank Suitable

Likely Fish-Only Tank Suitable


Sharks and rays do not fall into the category of Bony Fishes, which makes up the majority of this Fish Library. They belong to the Class Chondrichthyes, which includes nonbony fishes. Sharks and rays both fall into the Subclass Elasmobranchii, which includes jawed fishes with cartilaginous skeletons, multiple gill slits, skin covered with tiny tooth-like scales, and rows of regenerating teeth. Sharks fall into one of its two Superorders, Squalomorphii (Sharks). From there, some of the sharks of interest noted below fall into other various Orders and Families.

Most sharks are too large for the average aquarium, with the largest member, the whale shark (Rhiniodon typus ) attaining almost 60 feet. They have streamlined bodies and lack air bladders. Instead, they have a large two-lobed liver that helps maintain neutral buoyancy. Besides having a keen sense of smell and eyesight, sharks have renewable teeth, which many of us, including myself, would like to have! As teeth are worn-out or lost, new teeth from a back row move up to takes its place. They are also very sensitive to electrical impulses, as they can easily locate buried prey. However, this sensitivity can lead to their loss in the aquarium if equipped with a faulty heater, UV filter, or water pump.

They mostly require a large, well-filtered and well-oxygenated system with a fine grain sandbed, and few environmental obstructions even for the smallest members. Most succumb to poor husbandry skills. They cannot be treated with heavy metal solutions such as copper. Fresh seafood, such as shrimp, fish flesh, crab, scallops and freshwater mollies are welcomed. Do not house with large triggerfishes, angelfishes, wrasses, and pufferfishes as they can pick on the shark and cause skin/eye damage.

Whether you're a diver or aquarist, those shown below are for your edification, with some, if not most deserving to stay in the wild! For much more in-depth information on these creatures I suggest reading Aquarium Sharks & Rays, An Essential Guide to Their Selection, Keeping, and Natural History by Scott Michael, ISBN #1-890087-57-2.

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